reaction with cesium carbonate, the most basic of the alkali carbonates of the group I metals.' Carboxylic acids,2 phenol^,^ thiol^,^ sulfonamide^,^ some ureas,3 and 1,3-di- carbonyl compounds6 are deprotonated to form the cor- responding cesium salts. The choice of cesium carbonate rests on practical considerations, particularly the ease of